1. V. Gutlyanskii, V. Ryazanov, U. Srebro, and E. Yakubov, The Beltrami Equation: A Geometric Approach, Springer, New York, 2012.
2. J. Maly and O. Martio, “Luzin’s condition N and mappings of the class $$ {W}_{loc}^{1,n} $$,” J. Reine Angew. Math., 458, 19-36 (1995).
3. O. Martio, V. Ryazanov, U. Srebro, and E. Yakubov, Moduli in Modern Mapping Theory, Springer, New York, 2009.
4. V. Gutlyanskii, V. Ryazanov, U. Srebro, and E. Yakubov, “On recent advances in the degenerate Beltrami equations,” Ukr. Mat. Visn., 7(4), 467-515 (2010).
5. U. Srebro and E. Yakubov, “The Beltrami equation,” in: Handbook in Complex Analysis: Geometric function theory, Vol. 2, Elsevier, Amsterdam, 2005, pp. 555-597.